Modulation of the sleep electroencephalogram by estrogen replacement in postmenopausal women

OBJECTIVE: We performed an examination of the effects of estrogen replacement on the sleep electroencephalogram in postmenopausal women. STUDY DESIGN: A sleep electroencephalogram was recorded in 11 postmenopausal women with and without estrogen administered by skin patch (50 mu g of estradiol per day). RESULTS: Estrogen enhanced rapid-eye-movement sleep (50 +/- 4 vs 39 +/- 5 minutes, P <.05) and reduced time awake (12 +/- 5 vs 20 +/- 6 minutes, P<.05) during the first 2 sleep cycles. The normal decrease in slow-wave sleep and delta activity from the first to the second cycle tin percentage from the first cycle) was restored by estrogen (-56% +/- 9% vs -5% +/- 14% and -20% +/- 6% vs -2% +/- 5%; P <.05, respectively). Sigma electroencephalographic activity was increased by estrogen from the first to the second half of the night but decreased during baseline. CONCLUSION: Estrogen treatment after menopause can help to restore the normal sleep electroencephalogram pattern, which in turn might contribute to improved cognitive functioning.